Abstract: Affected by excavation disturbance or in-situ stress, the heterogeneity of surrounding rock is universal. Therefore, treating the permeability as a constant will reduce the accuracy of water inflow prediction. In view of this problem, a calculation model of water inrush in tunnel considering the heterogeneity of surrounding rock is constructed. Based on the equilibrium differential equation for seepage and Darcy's law, the calculation formula of water inrush and external water pressure of the structure is derived. Taylor's formula and its series expansion are used to degenerate and verify the analytical formula, and then the applicability of the formula is also analyzed. Finally, this model and the formula derivation are verified by comparing results with the measured data. Research shows that the decrease in the excavation disturbance can reduce the variability of the permeability of the surrounding rock of the tunnel, which can improve water resistance of the tunnel. Considering the influence of excavation disturbance on the permeability of the surrounding rock, the calculation error of the water head height at the outer edge of the supporting structure can be reduced from 14% to 6%. Considering the influence of ground stress on the permeability of the surrounding rock, the calculation error of water inflow can be reduced from 18.2% to 10.6%, which improves the prediction accuracy to a certain extent.

Key words: excavation disturbance, permeability, in-situ stress, water inflow prediction